Rotational characteristics of a drill string are important to many operations undertaken during the drilling process of a subterranean well. One example is drill string rotation rate which can vary along the length of the drill string due to, among other things, the natural flex of their materials of construction, drag caused by contact with sides of the wellbore, extreme downhole conditions and resistance to rotation experienced at the drill bit. Many tools along the drill string require rotational information in order to carry out their particular purposes. Accordingly, sensors are often provided locally, within a tool, or within the immediate vicinity of the tool, for monitoring different aspects of the drill string's rotation, and especially the drill string's rotational speed.
For any number of reasons, certain tools on the drill string may not have locally sensed or otherwise detected rotational information or data about the drill string, even though such information is either required by, or beneficial to operation of the particular tool. In some instances, sensors provided at the tool can malfunction or fail and cease to provide accurate rotational information. Still further, some materials from which tools are constructed can negatively affect sensors' abilities to function; for instance, sensors will often not work across certain metals. If these metals are used in a tool's construction, it may not be possible to include a sensor.